This study is focused on the attempt to answer questions about the mechanisms for the commitment of workers to political union activity, as well as about the way the political legitimacy process occurs in different spheres of the Brazilian trade union field. In order to answer such questions, two unions from the state of São Paulo were studied: the steelworkers' union, from the ABC region, and the telecommunications workers' union. There are some similarities between these unions, especially the fact that during the 90s, both of them went through the processes of economic restructuration and personnel renewal - including generational succession. It is also interesting to mention the similarity concerning the social origin of workers and trade unionists, mostly Northeastern unskilled migrants with low schooling levels. Concerning the differences between the workers, we observe that the constitution of the process of trade union legitimacy takes on distinct compositions, which result in distinct reactions to the changes in the two sectors. Even though they have faced equivalent social changes, each of these unions has its own different dynamics in the building of different militant legitimacies and in future unionists' actions.
trade unions; legitimacy; social route; political field; telecommunications; steel work